System and method for communicating data in a video system

ABSTRACT

A system and method of controlling a video camera arranged to provide a video signal on a transmission medium including: transmitting command data on the video transmission medium to the camera, and receiving response data from the camera over the video transmission medium during a single vertical blanking period of the video signal, improving controllability of dome type cameras. Using an encoding format with data with bit widths narrower than those conventionally used in UTC protocols, increases the usable transmission medium length for the system by allowing for longer propagation delays without errors caused by interference. A method of downloading data to a camera by disabling the video signal, and a method of self-instantiating camera functions are also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 10/395,296 filed Mar. 24, 2003, now U.S. Pat. No. 7,573,500,entitled SYSTEM AND METHOD FOR COMMUNICATING DATA IN A VIDEO SYSTEM, theentire disclosure of which is hereby expressly incorporated byreference.

FIELD OF THE INVENTION

The present invention relates to video surveillance systems employingremotely-controllable video cameras, and, more particularly, to a systemand method for facilitating bi-directional communication between videocameras and video camera control equipment.

BACKGROUND OF THE INVENTION

Video surveillance systems are conventionally configured asclosed-circuit systems wherein one or more video cameras controllablymonitor selected areas of interest. The video cameras may transmit videosignals over a cable to a control console at which the signals areswitched, viewed on monitors, etc. The cable over which the videosignals are transmitted may also be used for transmitting informationfrom the control console to the camera, video multiplexer or videoswitch. For example, commands may be sent from the control console orvideo switch for controlling pan-tilt-zoom (PTZ) features of a videodome camera, video source selection within a video switch, downloadingcamera, multiplexer or video switch software updates, etc.

Coaxial cable has been the traditional medium of choice for transmittinganalog video signals from the camera to the control console. The processof transmitting control data over the video transmission medium bydriving the control data in the opposite direction with respect to thevideo signals has commonly been referred to as “Up-The-Coax” (UTC)protocol. To prevent the system from acting on commands containingtransmission errors, conventional UTC solutions either repeattransmitted commands multiple times to provide redundant transmissions,or use bi-directional communication whereby an acknowledge handshakesignal is provided by the camera in response to a received command.

Filtering out corrupted commands typically requires the device receivingthe command to verify the checksum, parity, or CRC of the transmittedsignal. Redundant transmission methods can require consecutive,identical commands before acting on them. However, verification usingthese techniques can be impossible when multiple messages are corrupted.Current bi-directional schemes address this issue by transmitting acommand, e.g. to the camera, during one vertical interval of the videosignal and transmitting an acknowledge (ACK) reply message back to thecontroller during the next vertical interval. If the reply messageindicates a negative acknowledge (NAK), the controller would re-transmitthe command on the next vertical interval. This sequence causes alatency of two vertical time periods.

Both redundant and bi-directional UTC protocols have typically beenlimited to transmitting/receiving four bytes of data per vertical periodof the video signal. This command size restriction has made itimpractical to pack variable speed command data for all axes of a videodome camera into a single transmission. With the limited byte count,simultaneous panning and tilting in a video dome camera has requiredmultiple commands.

Some UTC protocols have transmitted 16-bit words in each of twohorizontal line periods of the video signal. These schemes use shorterpulse widths to allow the command word to fit between two horizontalpulses. When UTC commands are transmitted over long distances, thepulses have slower rise and fall times and are delayed with respect tothe video generated at the receiving end. The slower rise and fall timesplace a practical limit on how narrow the pulse widths may be tofacilitate detection by low cost detection circuits.

The pulse widths conventionally used when transmitting 16-bit words in ahorizontal line require the words to occupy most of a horizontal period.To prevent the last pulse of a UTC command from interfering with thenext horizontal sync pulse from the camera, the length of thetransmission cable must be limited. For example, with RG59 coaxialcable, the length must be less than 2500 feet. Wider pulses are not aseasily degraded beyond usable limits due to rise and fall times, howeverwider pulses reduce the usable cable length because they reduce themargin between the end of a command word and the following horizontalsync pulse.

The useful length can be stretched by starting the transmission beforethe color burst signal. Corrupting the color-burst signal duringvertical blanking may have a noticeable effect on the image depending onthe system configuration. Overlapping the command with the color-burstcan require a more sophisticated detection circuit at the camera end todistinguish weak command pulses. Reply data transmitted by the cameradevice is subject to the same cable related delays as the video signal.

Also, known systems have required complex repeater configurations forre-driving the video signal with embedded reply data from the videodome, while capturing, buffering and re-inserting the UTC data from thecontroller in the next vertical interval. It is desirable to allowlonger runs of transmission media without requiring expensive repeaters,simply to avoid UTC command interference. For systems with very longtransmission media and reasonable signal loss, e.g. fiber-optic cable,it is desirable for the device that is supplying the video signal tohave a receiver capable of accurately separating command pulses thatoverlap horizontal sync pulses or color burst that is being transmittedin the opposite direction. Some UTC protocols only transmit one byte ofdata per horizontal line. This smaller data packet allows longertransmission delays without interference with the horizontal sync.Single byte packets can also be encoded with wider pulse widths makingthem more tolerant of attenuation and the longer rise-fall timesassociated with long or lower-cost, lower-quality cable runs. However,with the limited number of horizontal lines available for bi-directionalcommunication during a single vertical blanking period, the single byteapproach limits the total command size to half that available with16-bit per horizontal schemes.

Another difficulty associated with conventional UTC protocols is thatthey render downloading large firmware updates through a series of4-byte UTC commands impractical. In order to add new functions tocurrent dome control systems, an operator uses pre-numbered functionkeys or multiple key combinations to send commands to control the newfunctions. Most controllers do not provide enough spare function keysfor future functions. Using multiple key combinations is cumbersome dueto the difficulty in memorizing the combinations. Moreover, the commonand most frequently used commands typically include dedicated andclearly marked keys. New special functions tend to be used infrequently,and, as such, would benefit the most from labels or help screens.

The functions that need to be performed by the function keys or keysequences are not known at the time of manufacture of the controller andare, therefore, not labeled on the controller. Some controllers havescreens that can be used to display labels or help for the functionkeys, but the functions must still be known at the time of manufacture,or updates for the controllers must be installed as new features areadded. When new video domes are developed with new features that requirenew commands, the controllers in the field must be upgraded or theoperators will be forced to memorize keys or key sequences to use thenew features.

Conventional UTC techniques are therefore inefficient in thetransmission of control commands and data over a transmission medium toa video dome, switch, recorder, etc. In fact, simple movement control ofvideo dome-type devices has noticeable latency. Also transmission of newsoftware updates is slow enough to be deemed impractical, and addingcontrol functions to an existing system is difficult.

Accordingly, there is a need for improving the speed of downloadingcontrol commands and data over a transmission medium to a video dome,switch, recorder, or other video surveillance system device. There isalso a need for a facile and efficient method implementing new functionsin a video system controller.

SUMMARY OF THE INVENTION

A system consistent with the invention includes a variety of aspects.According to one aspect of the invention there is provided a method ofcontrolling a controllable video device, e.g. a video camera, configuredto provide a video signal on a transmission medium. The method includes:transmitting command data to the controllable video device over thetransmission medium during a vertical blanking period of the videosignal; receiving the command data at the controllable video device; andtransmitting response data from the controllable video device over thetransmission medium during the same vertical blanking period in responseto the command data. A video system including a controllable videodevice and a command source, e.g. a controller, configured to perform amethod according to this aspect is also provided.

According to another aspect of the invention, there is provided a methodof controlling a controllable video device configured to provide a videosignal on a transmission medium including: transmitting command data tothe controllable video device over the transmission medium during atleast one horizontal line in a vertical blanking period of the videosignal, the data including a plurality of encoded bits, each of the bitshaving an encoding format wherein a first logic value is represented bypresence of a transition during a bit period and a second logic value isrepresented by absence of a transition during said bit period.Advantageously, using such a data format can reduce bit period andoverall packet length to ⅔ that of pulse width encoding techniques whilemaintaining the same minimum pulse width, providing a means fortransmitting over a longer transmission medium. A video system includinga command source configured to perform a method according to thisadditional aspect is also provided.

According to a further aspect of the invention, there is provided amethod of downloading data to a controllable video device configured toprovide a video signal on a transmission medium. The method includes:disabling at least an active portion of the video signal during at leastone vertical field of the video signal; and transmitting the data to thecontrollable video device over the transmission medium during a timewhen the active portion of the video signal is disabled. A video systemincluding a controllable video device and a command source configured toperform a method according to this further aspect is also provided.

According to yet another aspect of the invention there is provided amethod of controlling a controllable video device configured to providea video signal on a transmission medium. The method includes:transmitting a function command from a command source to thecontrollable video device over the transmission medium; transmittingreply data to the command source, the reply data being in response tothe function command and being configured to cause display, e.g. at thecontroller or other device, of a plurality of available functions forthe controllable video device; transmitting a function start command tothe controllable video device in response to the reply data, thefunction start command being configured to cause the controllable videodevice to perform at least one of the plurality of available functions.A video system including a controllable video device and a commandsource configured to perform a method according to this aspect is alsoprovided.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, together with otherobjects, features and advantages, reference should be made to thefollowing detailed description which should be read in conjunction withthe following figures wherein like numerals represent like parts:

FIG. 1 is a simplified block diagram of an exemplary embodiment of aclosed-circuit video surveillance system in which a method consistentwith the present invention is applied;

FIG. 2 is an illustration of an exemplary command and response dataformat consistent with the invention;

FIG. 3 is an illustration of an exemplary camera movement command dataformat consistent with the invention;

FIG. 4 is an illustration of an exemplary camera movement response dataformat consistent with the invention;

FIG. 5A is a plot of voltage vs. time illustrating exemplary encodingschemes useful in a system consistent with the present invention;

FIG. 5B is a plot of voltage vs. time illustrating exemplary timing forcommand and response data in a system consistent with the inventionrelative to a horizontal sync pulse;

FIG. 6 is a block flow diagram of an exemplary method of controlling avideo camera consistent with the present invention;

FIG. 7 is a block flow diagram of an exemplary method of downloadingdata to a video camera consistent with the present invention;

FIG. 8 is a block flow diagram of an exemplary self-instantiation methodconsistent with the present invention; and

FIG. 9 is perspective view of an exemplary controller consistent withthe present invention.

DETAILED DESCRIPTION

The present invention will be described herein in connection withvarious exemplary embodiments thereof. It is to be understood that theembodiments described herein are presented by way of illustration, notof limitation. The present invention may be incorporated into a widevariety of systems requiring bi-directional communication over atransmission cable without departing from the spirit and scope of theinvention. In addition, although coaxial cable has been the traditionalmedium of choice for transmitting analog video signals, those skilled inthe art will recognize that other media such as twisted pair wire, fiberoptic cable, etc. are becoming common choices. The present invention isnot limited to any particular transmission medium. As such, a protocolconsistent with the invention may be more properly described as an“Up-The-Cable” protocol to indicate its utility in connection with anytype of transmission medium.

Turning now to FIG. 1, there is illustrated, in simplified block diagramform, an exemplary closed circuit video surveillance system 10consistent with the invention. The system 10 includes: a system controldevice or controller 12 for controlling operation of one or more videocameras. Those skilled in the art will recognize that a varietycontrollable video devices e.g., video matrix switches, videomultiplexers, video recorders and etc., may be controlled by otherdevices, and that the controllable devices may also be configured tocontrol other controllable devices over the same video connection orover separate connections. For simplification of the exemplaryembodiments illustrated herein, reference to communications between avideo command source and a video controllable device use a videocontroller as a generic command source and a video camera or video domeas a generic controllable video device.

With continued reference to FIG. 1, for simplicity and ease ofexplanation only one video camera 14 is explicitly illustrated. Thesystem 10 also includes a number of video monitors, which are not shown,and a matrix switch 16 for routing video signals from cameras selectedthrough the control device 12 so that the video signals from theselected cameras are displayed on monitors which are also selectedthrough the control device 12.

Each of the cameras, including camera 14, is connected to the matrixswitch 16 by means of a transmission medium. Again, for simplicity, thetransmission medium in FIG. 1 is a cable 18 associated with the camera14. The transmission medium may however be any medium capable oftransmitting video signals from the camera and command signals to thecamera, such as a coaxial cable, twisted pair wire, fiber optic cable,air, etc.

The camera 14 may be a video dome-type camera in which the cameraoperating characteristics including direction of view, zoom condition,focus, etc., can be changed by remote control. In particular, controlsignals are transmitted to the camera 14. In response to the controlsignals received at the camera, motors are controlled to change thecamera's operating characteristics.

A control code receiver and motor driver circuit 20 may be provided,either as an integral part of the camera or as a separate component.Video signals generated by the camera 14 may be output from the camera14 to the circuit 20, which in turn couples the video signals to thecable 18 for transmission to the matrix switch 16. It is to beunderstood that reference to transmission of data or signals to and fromthe camera are intended as indicating transmission to and from thecircuit 20 over the cable 18 on which the video signal is provided,regardless of whether the circuit 20 is integral with the camera orphysically separate therefrom.

Camera control signals generated at the control device 12 are coupledonto the coax cable 18 by the matrix switch 16 for transmission to thecamera 14. More specifically, the control signals transmitted throughthe cable 18 from the matrix switch 16 are received and detected at thereceiver circuit 20 and, after suitable conditioning, are transmittedfrom the receiver circuit 20 to control the motors (not separatelyshown) associated with the camera 14. As will also be seen, the receivercircuit 20 may also include appropriate circuitry for compensating forlosses and frequency dependent effects resulting from transmission ofthe video and control signals through the coax cable 18.

As will be recognized by those skilled in the art, a video signalprovides information for causing an image to be displayed on a videoscreen or monitor one horizontal line at a time. The image is started atthe top left of the video screen and horizontal lines are written fromleft to right in response to the video signal. When one line is ended,the next horizontal line is written just below the previous line. In oneapproach, this process of writing horizontal lines in response to thevideo signal is repeated until a first video frame, e.g. 525 horizontallines, is complete. The video signal then causes the image to restart atthe top of the video screen to begin writing the next video frame.

In a more common interlaced approach, each frame is divided intoseparate fields, each with half the picture information. The first fieldmay contain all the odd numbered horizontal lines, and the second fieldmay include all even numbered horizontal lines. After one field, e.g.all odd-numbered lines, is scanned from top to bottom of the screen, thesecond field, e.g. all even numbered lines, is scanned from top tobottom of the screen. This process is repeated, e.g. at 30 frames persecond, to produce the video image.

When each horizontal line is scanned, the scan is returned to the leftside of the screen without producing an image on the screen. This isaccomplished during the horizontal blanking interval by bringing thevideo signal to a blanking level. Likewise, after all horizontal linesare scanned for a frame and/or field, the scan is returned from thebottom of the screen to the top of the screen without producing animage. This is accomplished during the vertical blanking interval bybringing the video signal to a blanking level. During the verticalblanking period, a number of horizontal lines are scanned out of theviewing area at the top of the video screen without producing an image.For example, video according to the standard set by the NationalTelevision Standards Committee (NTSC) includes 525 scanning lines, but42 of the horizontal lines at the top of the screen, i.e. 21 for eachvertical field, are commonly blanked out during the vertical blankingperiod.

Advantageously, a system and method consistent with the presentinvention accomplishes bi-directional communication on the cable 18 bytransmitting up to 8 bytes of data in both directions, i.e. to and fromthe camera, during any vertical blanking interval of the video signal.Use of 8 data bytes for a command signal from the controller allows an 8byte acknowledge reply from the camera to immediately follow the commandsignal in the same vertical blanking period. This reduces the commandlatency attributed to current UTC handshake protocols by 50%, therebysignificantly improving real time controllability of video cameras, suchas video dome-type devices.

Also an 8-byte command signal provides enough space for a command headerbyte, a CRC check or checksum byte, and simultaneous commands for allaxes of a video dome-type device, including variable PTZ. Thisdrastically reduces latency compared to conventional solutions. In fact,controlling three axes simultaneously with a single command signal andsending acknowledge replies during the same vertical blanking periodreduces latency to about 1/16.sup.th of conventional protocols.

Turning now to FIG. 2, there is illustrated an exemplary command signalformat 200 consistent with the invention. As shown, the command signalincludes 8 bytes of data, i.e. two bytes transmitted on each ofhorizontal line numbers 11-14 during the vertical blanking period. Thehorizontal line numbers 202 referenced in FIG. 2 correspond to NTSCcommon line numbers, where the end of line #3 on odd fields, or themiddle of line #3 on even fields, corresponds to the start of thevertical blanking pulse It is to be understood, however, that thepresent invention has applicability to any video signal format,including NTSC/EIA and PAL/CCIT formats.

For example, horizontal lines in Phase Alternation by Line (PAL) systemsare commonly numbered from 1-625, with the vertical blanking pulse atthe start of line 1 for even fields or the middle of line 313 for oddfields. To convert the illustrated data frame for use in a PAL videostandard, commands could be output on the identified NTSC horizontalline minus 3 for even fields, and plus 310 for odd fields. It is to beunderstood that the data transmitted on line numbers 11-14, chosen asthe first implementation of this protocol and used to illustrate thisinvention, can be output on other line combinations, such as 10-13,12-15 or any other grouping chosen so as not to interfere withtransmitted video quality.

The illustrated frame structure 200 includes a first byte 204 includingbits 15-8, and second command byte 206 transmitted on horizontal line11. Line 12 includes third 208 and fourth 210 command bytes, and line 13includes fifth 212 and sixth 214 command bytes. A seventh command byte216 is transmitted on line 14 along with a Check sum byte 218.

The first byte 204 on line 11 may include a four bit Message Typeindicator 220 and a four bit Remaining Packets indicator 222. TheMessage Type indicator 220 may be used to transmit information to thevideo camera/dome indicating the type of command being transmitted.Table 1 below illustrates exemplary Message Type commands along with theexemplary associated binary values for the bits in the Message Typesection 220, i.e. bits 15-12.

TABLE-US-00001 TABLE 1 Message Type Binary Camera Movement Command 0010Camera Movement Command Response 0011 Set Time and Date Command 0100 SetTime and Date Command Response 0101 Get Dome Configuration InformationRequest 0110 Dome Configuration Information Response 0111

Those skilled in the art will recognize that the controller and videocamera/dome may be configured to communicate a variety of message typesdepending system functionality. The four bit Message Type section leavesroom to associate additional message types with particular bit patterns.

The Remaining Packets indicator 222, i.e. bits 11-8 in the first byte204 may include a binary number indicating the number of subsequent8-byte packets in the current command or response. This information maybe used by the camera/dome to determine the number of packets to bereceived. The second 206 through seventh 216 bytes in a command mayinclude command data for causing the camera/dome to perform the specificcommand, or, in the case of response, specific data indicating that thecommand was fully received, indicating alarm status, and/or indicatingcamera/dome configuration information. The Check Sum byte 218 may beformed in a variety of ways known to those skilled in the art, e.g. CRCor by simply performing binary addition on the first seven bytes.

FIG. 3 illustrates an exemplary camera movement command 300 formatted inthe manner illustrated in FIG. 2. The illustrated camera movementcommand can be transmitted to provide full camera control, e.g. controlfor all axes of movement in a dome-type camera, in one 8-byte packet.Proportional control of pan and tilt are embedded with single speed orramped speed controls for zoom, focus and iris and any other specialcamera features selected by the operator.

On line 11 of the command illustrated in FIG. 3, a message typeindicator 220 a containing 0010 indicates that the command is a cameramovement command, and the Remaining Packet bits indicate that thecommand includes no remaining packets. Bits 0-5 on line 11 control FocusIn, Focus Out, Zoom In, Zoom Out, Iris Open, and Iris Close, camerafunctions, respectively. Setting any of these bits to a one may begincamera movement in the associated function. Bits 6 and 7 on line 11 maybe are reserved for expansion.

In line 12 the third and fourth command bytes include tilt and pancontrol data. Bit 15 on line 12 indicates tilt direction, with a one inthis location indicating a tilt up and a zero indicating a tilt down.Tilt speed is indicated in bits 14-8 of third byte. Bit 7 on line 12indicates pan direction, with a one in this location indicating a panleft and a zero indicating a pan right Pan speed is indicated in bits6-0 of fourth byte.

Line 13 includes Rail Control data in the fifth byte 212 a and SpecialDome Function data in the sixth byte 214 a. The Special Dome Functiondata in the sixth byte may initiate a special dome function inconnection with the transmitted command. Those skilled in the art willrecognize that video camera/dome may be configured to perform a varietyof Special Dome functions including: reset dome, exit and enter domemenu, flip (pan 180 degrees), resume auto iris and auto focus, run selfinstantiating function (described below), start apple peel pattern, runa predefined pattern, etc.

Line 14 includes Auxiliary Data in the seventh byte 216 a and a CheckSum 218 a. The Auxiliary Data may contain an operand associated with aSpecial Dome Function indicated in the sixth byte. For example, a resetdome command indicated in the sixth byte may require a particular bitsequence in the Auxiliary Data field to prevent inadvertent occurrencesof the reset command.

FIG. 4 illustrates an exemplary camera movement command response. Theillustrated camera movement command response may be transmitted from thecamera in response to, for example, the camera movement commandillustrated in FIG. 3. In general, a response signal has the same formatas a command signal, but in this exemplary embodiment is transmitted onhorizontal lines 16-19 during the same vertical blanking period as thecommand. In the illustrated exemplary embodiment, no command or responsedata is transmitted on line 15 to accommodate transmission delays whentransmitting up to 16 miles, e.g. on fiber links. Those skilled in theart will, however, recognize that data may be transmitted without anyskipped lines, if system transmission delays are not significant.

As in the command signal format, the response signal format 400 includestwo bytes transmitted on each line with Message Type 226 b and RemainingPacket 222 b data in the first byte (on line 16 for a response), and aCheck Sum 218 b in the eighth byte (line 19). The second through seventhbytes include data particular to the transmitted response, and can beused to indicate current alarm input and camera/dome status informationthereby eliminating the need to send a periodic, dedicated, pollingcommand for alarms or dome status information. Eliminating separatepolling commands normally required to maintain current dome statusfurther reduces control command latency, improving controllability ofthe system.

In the illustrated exemplary response, line 16 includes a Message Type220 b containing 0011 indicating that the response is a movement commandresponse, and the Remaining Packet bits 222 b indicate that the responseincludes no remaining packets. Bits 7-4 on line 16 indicate the numberof remaining packets from the last command, and bit 3 is reserved. Bit 2is a PR bit indicating when there is a pattern running. The PR bit maybe a one when a pattern command is processed and running, and a zerowhen the pattern is finished. Bit 1 is an ACK bit indicating that apacket was received with a correct checksum during the current verticalinterval, and bit 0 may be a NAK bit indicating that a packet wasreceived with an incorrect check sum during the current verticalinterval.

Line 17 includes Alarm Input state data in bits 15-12 and the Complimentof the Alarm Input States on bits 11-8, which provide alarm redundancy,preventing false alarming. The fourth byte 210 b on line 17 and thefifth 212 b and sixth 214 b bytes on line 18 are reserved. The seventhbyte 216 b on line 19 includes a check sum of the last received command,and the eighth byte is the Check Sum 218 b of the response packet.

Since all movement control commands are provided in a single cameramovement command, if no command is received by the camera within apredefined period of time, the camera may be programmed to stop allmovement. For example, in one embodiment if no command is receivedwithin about 300 ms, the camera may be configured to stop all movement.This eliminates the possibility that the camera will continually executea received command when communication is disrupted, and avoids the needto send separate stop commands from the controller to arrest cameramovement.

Those skilled in the art will recognize that command and responsesignals may be formatted in a variety of ways to communicate thecommands and responses available or desired in a particular system. Ingeneral, providing 8 bytes of data for a command and 8 bytes of data fora response in the same vertical field advantageously yields an effectivebit rate in both directions of 3840 bps (4.times.16.times.60) for anNTSC system (60 Hz) and 3200 bps (4.times.16.times.50) for PAL systems(50 hz). This provides a significant improvement in command responsetime and latency compared to conventional UTC solutions resulting in avast improvement in the real-time controllability of video devices.

Those skilled in the art will recognize that a system and methodconsistent with the invention may be implemented by appropriatelyprogramming the controller and camera to transmit and receive thecommand and response signals in response to the video signal. Data maybe encoded by the camera and receiver in a variety of formats. FIG. 5Aillustrates a pulse-width modulated encoding format, as well asBi-Phase-Mark, Bi-Phase-Space, and Manchester encoding schemes. Theencoded data in FIG. 5A, for example, corresponds to a 01001110010110bit sequence. As shown, the pulse-width modulated data includes bitshaving a value represented by pulse width P. In contrast, theManchester, Bi-Phase-Mark, Bi-Phase-Space encoding schemes encode bitvalue by the presence or absence of a transition, e.g., T1, T2, T3,during a bit period.

Advantageously, encoding data with a Bi-Phase-Space (FM0), Bi-Phase-Mark(FM 1), Manchester or similar encoding, allows the bit widths to bereduced to ⅔ compared with simple pulse width encoding schemes, whilestill having the same minimum high and low pulse widths. Reducing thebit widths using these data encoding formats reduces the period of a16-bit encoded word from 48 μs to 32 μs. This allows the length of thecable 18 to be increased significantly. For example, if the propagationrate in the chosen medium is 1.55 ns per foot, using FM0 encoding wouldallow 10,322 feet of extra cable without causing interference with thenext horizontal sync pulse. It is noted that protocols such as FM0 andBi-Phase have an advantage over Manchester encoding schemes, in that theleading edge of the first pulse can be defined as the leading boundaryof the first bit cell and the first bit can be either polarity.

The controller may be configured to transmit a command signal, e.g. oncable 18, during a vertical blanking period of the video signal. Thecommand signal may include four sixteen bit words, as described above,following the horizontal sync pulse on lines 11-14. The camera may beconfigured to transmit a response to the command signal in four sixteenbit words following the horizontal sync pulse on lines 16-19 during thesame vertical blanking period as the command.

In one exemplary embodiment, as shown in FIG. 5B, the data may beFM0/Bi-Phase Space encoded with period P of 2 μs per bit, and with theleading edge 500 of the first bit 502 being a rising edge occurring 9.7μs from the leading edge 504 of the horizontal sync pulse 506, plus orminus 50 ns. In the FM0 or Bi-Phase Space encoding scheme, the data bitpolarity may be encoded by the presence or absence of a transition inthe middle of the bit time, with a “1” indicated by the absence of atransition and a “0” indicated by a transition in the center of the bittime. The FM0 data in FIG. 5B, for example, corresponds to a commandpattern beginning with a 110011 sequence. For commands or responses, theFM0 high state may by 0.714V above the blanking level. The specificvoltage used in replies should be enough lower than a white video levelso as not to adversely affect the AGC circuits in common monitors. Thecommand or response signal may either remain at the blanking level orreturn to the blanking level at the end of the last bit on eachhorizontal line.

In such embodiment, transmitted data from the camera or controller maybe within plus or minus 50 ns of the bit timing so that each bit may beused for synchronization. With this tolerance, accumulative toleranceover the length of a 16-bit word would be a maximum of 800 ns from thefirst pulse 502 to the end of the last pulse. For example, a transitiondetected inside a window of 0.5 μs to 1.5 μs measured from thetransition at the leading edge of a bit cell may be interpreted as azero. Outside of this window in the center of a bit time, a transitionmay be interpreted as the transition at the start of the next bit. Thedetectors at both the camera and controller ends may start looking forthe leading edge of the first pulse about 8.5 μs after the leading edge,e.g. 504, of the horizontal sync pulse, and continue looking for thefirst edge until about 31.5 μs after the leading edge. This allows amaximum propagation delay due to line length without corrupting the lastpulse with the next horizontal sync pulse.

FIG. 6 is a block flow diagram of a method 600 consistent with oneexemplary embodiment of the invention. The block flow diagrams usedherein to describe various embodiments include particular sequences ofsteps. It can be appreciated, however, that the sequence of steps merelyprovides an example of how the general functionality described hereincan be implemented. Further, each sequence of steps does not have to beexecuted in the order presented unless otherwise indicated.

In the illustrated embodiment, bi-directional data communication in avideo system may be accomplished in a manner consistent with theinvention by awaiting for 602 the vertical blanking period of a videosignal transmitted on a transmission medium, e.g. as indicated by thevertical sync pulse. During the vertical blanking period a command maybe transmitted 604 to the camera/dome on the transmission medium. Thecommand may be received 606 at the camera/dome, and the camera maytransmit a response 608 on the transmission medium during the verticalblanking period in which the command was transmitted. A command signalof 8 bytes may be transmitted from the controller to the camera, e.g. asfour sixteen bit words on each of horizontal lines 11-14 during thevertical blanking period. In response to the command signal, an 8 byteresponse signal may be transmitted from the camera to the controller. Toaccommodate line delay, the response may be delayed by one or morehorizontal lines. For example, the response may be transmitted as foursixteen bit words on each of horizontal lines 16-19.

A system consistent with the invention, e.g. system 100, may also beconfigured to facilitate download of large blocks of data to a videocamera from a controller at a high data rate. Downloading data to avideo camera/dome is often required in video systems to accommodatefirmware updates, e.g. updates to the video camera/dome firmware tofacilitate new functionality. Conventional solutions for downloadingsuch data have followed the traditional approaches for transmittingcommand and/or response data, i.e. data has been transmitted using theUTC command signal protocol regardless of its size or purpose. Fordownloading large blocks of data, however, the conventional UTCprotocols, e.g. using 4-byte UTC commands in each vertical blankingperiod, have not provided high data rate.

Of course, if data rate is not a serious concern in a particular system,data could be transferred by replacing the command and/or responsesignals consistent with the invention with data. This would at leastallow a data rate improvement over conventional methods. Consistent withthe present invention, however, a very high data rate may beaccomplished by gating off at least a portion of the video signal andcontinuously transmitting data.

FIG. 7 is a block flow diagram of an exemplary embodiment of a method700 of downloading data to a video camera/dome consistent with theinvention. As shown, the large blocks of data may be downloaded from acontroller to a video camera/dome by disabling 702 at least a portion ofthe video signal from the video camera during at least one verticalfield until the bi-directional communication is complete. The videosignal that has been disabled may then be replaced with data downloaded704 from the controller to the camera on the same transmission mediumnormally used for the video signal. Once the download is complete, thevideo signal from the camera may be restored 706.

In one embodiment, to maintain video synchronization during the downloadonly the active video signal, i.e. the entire video signal except thehorizontal and vertical sync pulses, may be disabled during the verticalfield. To disable the active video, the camera may replace the activevideo with a steady black level in response to a command from thecontroller indicating that data is to be downloaded. The controller maythen replace the active video signal with data, e.g. 16-bit words,transmitted on each of the active video lines in the field. In an NTSCinterlaced system, this would allow transmitting data on each of the 247active video lines in each vertical field. A resulting data rate for anNTSC or PAL system would be approximately 237 Kbps (NTSC:247lines/field.times.16 bits/line.times.60 fields/sec orPAL:297.times.16.times.50). While this approach provides a significantimprovement compared to current methods of downloading in a UTCenvironment, the communication pulses inserted in the entire activevideo can render the video unusable for normal operation. Accordingly,completely disabling the video signal during the download may bepreferable.

The video signal can be completely disabled if normal videosynchronization is not required or another surrogate synchronizationmethod is implemented. When the video signal is completely disabled, thecamera could be configured to use the video transmission media as adedicated, point-to-point, bi-directional data communications media,e.g. by appropriate configuration of standard UARTs, SCC controllers,etc. in the controller and camera. This approach allows very high dataspeed transfers of large data packets, limited only by the datacommunication technology used.

A video system consistent with the invention may also be configured toprovide self-instantiation of special camera/dome function commandswhereby control and online help for future camera/dome functions may beadded without updating the system controllers. It is to be understoodthat self-instantiation as described herein may be implementedindependently of the communication method between control equipment andthe camera equipment. Self-instantiation method can be implemented insystems with separate control and video cables, and/or in systems basedon Radio Frequency or Infra-Red communications.

Self-instantiation of special dome function commands provides a simplemethod to add control and online help for future dome functions withoutupdating the system controllers. FIG. 8 is a block flow diagram of anexemplary embodiment of a method 800 for performing self-instantiationof special dome functions consistent with the invention. As shown,self-instantiation may be accomplished by sending 802 a special domefunction command from the controller to the camera e.g. by including anappropriate bit sequence in the sixth byte 214 a of the command signalformat 300 illustrated in FIG. 3. The camera may be configured toreceive 804 and respond 806 to the special dome function command bysending a reply which causes the controller to display a menu of camerafunctions. The operator can select one of the functions displayed on thecontroller, triggering a command 808 to be sent to the camera to causethe camera to perform the corresponding special function. Camerasprogrammed to support self-instantiation consistent with the inventioncan download new special function help information to controllers on anas needed basis, thereby completely eliminating the need to updatecontrollers as new functions become available on new camera/domesystems.

In an exemplary embodiment, a controller 12 a consistent with theinvention may include an interface having a user interface control, suchas a Dome Function button 904, and a numeric keypad 902, as shown, forexample in FIG. 9. Activating the user interface control, e.g.depressing the Dome Function button, without a previous numeric entry onthe keypad 902 may cause the self-instantiating command to be sent tothe camera/dome, triggering the dome to display a numbered menu list ofcurrent available special dome control functions (such as flip, togglecut filter in/out, reset auto focus/iris, enter dome set up mode, togglewide dynamic range mode, and etc.). This allows controllers that are notequipped with a help display screen to facilitate the special functioncommands. The larger on-screen text overlay capabilities available inmost domes and some cameras may be a more user friendly way ofdisplaying the special function help information, even if a display isavailable at the controller. In cases where a display is not availableat the controller, the list of available commands may be displayed onanother device, e.g. by a printout from a printer attached to thesystem.

Each item on the menu list may be displayed with an associated numericvalue, e.g. 1-255. Entering a numeric value on the keypad 902 associatedwith a specific listed function, followed by depressing the DomeFunction button 904, may trigger the controller to send the specialfunction command and the entered number to the dome. When the domereceives the special dome function command with a valid number itperforms the selected function, regardless of whether the menu waspreviously displayed. If the menu was displayed, the dome may also clearthe menu from the controller screen in response to the command. When thefunction is complete, the dome may resume normal operation. Pressing theDome Function button 904 while the menu is being displayed, without anumeric entry, may clear the menu from the screen and resume normaloperation.

Those skilled in the art will recognize that a user interface controlsuch as the Dome Function button 904 can take a variety of forms, e.g.an onscreen button in a graphical user interface or a hard key on aconventional keyboard controller, to allow operation with any type ofcontroller interface. For controllers with a local text display 906 onthe user interface, the numbered menu can be retrieved from the dome forlocal display on the controller using two-way data communication.Revised dome function button labels can then be continually displayed atthe controller 12 a, eliminating the need to pull-up the specialfunction menu on the video display.

Onscreen dome menus may also be configured to allow re-allocation of thedefault numerical values associated with available special functions.This allows new functions to be implemented without needing to usecryptic function keys or multiple key combinations to obtain new andneeded control codes. An operator can simply press the Dome Function keyto view a list of numbered functions. Since functions can be selectedwithout the menu of functions being displayed first, it will allow usersto more quickly select functions once they know the appropriate number.

It will be appreciated that the functionality described for theembodiments of the invention may be implemented in the videocamera/dome, controller or other video system components using hardware,software, or a combination of hardware and software, and well-knownsignal processing techniques. If implemented in software, a processorand machine-readable medium is required. The processor can be any typeof processor capable of providing the speed and functionality requiredby the embodiments of the invention. For example, the processor could bea process from the Pentium® family of processors made by IntelCorporation, or the family of processors made by Motorola.Machine-readable media include any media capable of storing instructionsadapted to be executed by a processor. Some examples of such mediainclude, but are not limited to, read-only memory (ROM), random-accessmemory (RAM), programmable ROM (PROM), erasable programmable ROM(EPROM), electronically erasable programmable ROM (EEPROM), dynamic RAM(DRAM), magnetic disk (e.g. floppy disk and hard drive), optical disk(e.g. CD-ROM), and any other device that can store digital information.In one embodiment, the instructions are stored on the medium in acompressed and/or encrypted format.

As used herein, the phrase “adapted to be executed by a processor” ismeant to encompass instructions stored in a compressed and/or encryptedformat, as well as instructions that have to be compiled or installed byan installer before being executed by the processor. Further theprocessor and machine-readable medium may be part of a larger systemthat may contain various combinations of machine-readable storagedevices through various I/O controllers, which are accessible by theprocessor and which are capable of storing a combination of computerprogram instructions and data.

There is thus provided a system and method whereby a video cameracommand providing full camera control is provided over a video signaltransmission medium to a video camera/dome during a vertical blankingperiod of a video signal. A response is provided by the camera/domeduring the same vertical blanking period in which the command wastransmitted. This significantly improves command response time, reducesalarm latency and lowers system communications overhead compared toprior UTC solutions, thereby dramatically improving real-timecontrollability of video camera/dome-type devices. A system and methodconsistent with the invention may also implement an encoding scheme withreduced pulse width compared to conventional approaches, therebyfacilitating a significant extension of the useful length oftransmission media used for both bi-directional control and to transmitvideo signal.

According to another aspect of the invention, a video system may beconfigured to allow download of large blocks of data at a very high datarate by disabling at least a portion of the video signal andcontinuously transmitting data. This significantly improves theefficiency of downloading large firmware updates to video cameras/domes.Also, a system consistent with the invention may be configured toprovide a self-instantiation function, whereby new video camera/domefunctions may be implemented without requiring use of cryptic functionkeys or multiple key combinations to obtain new and needed controlcodes.

In another aspect of the invention, downloading large blocks of data toaccommodate firmware updates to remotely-controllable video surveillancesystems can be accomplished by disabling the active video signal duringthe entire vertical field. This allows nearly continuous transmission ofdata from the controlling device to a video device, such as a video dometype device. If it is desired to maintain video synchronization duringdata transfer, vertical and horizontal sync pulses can be passed fromthe video device with only the active portion of the video disabled toallow UTC data transmission. However, for optimum data transferefficiency, data can be transmitted without regard to the horizontalline position.

If normal system video synchronization is not required or anothersynchronization method implemented, standard UARTs, SCC controllers orthe like can be configured to use the video transmission media as adedicated, point-to-point, bi-directional data communications media.This arrangement facilitates very high speed data transfers, limitedonly by the current data communication technology used.

The embodiments that have been described herein, however, are but someof the several which utilize this invention and are set forth here byway of illustration but not of limitation. For example, exemplarycommand and response formats including an 8-byte command and 8-byteresponse are discussed herein. However, commands and/or responsesincluding a different number of bytes or different format may betransmitted during a single vertical blanking period in a mannerconsistent with the invention. In addition, various features andadvantages described herein may be combined or used separately. It isobvious that many other embodiments, which will be readily apparent tothose skilled in the art, may be made without departing materially fromthe spirit and scope of the invention.

1. A method of downloading data to a controllable video deviceconfigured to provide a video signal on a transmission medium, themethod comprising: disabling at least an active portion of the videosignal during said at least one vertical field of the video signal; andtransmitting the data in separate portions to the controllable videodevice over the transmission medium during a time when said activeportion of said video signal is disabled, each of said separate portionsbeing transmitted on an associated one of a plurality of horizontallines in said vertical field, wherein each of said separate portionscomprises a plurality of bits encoded in a bit period, a first logicvalue of each of said bits being represented by presence of a transitionduring said bit period and a second logic value of each of said bitsbeing represented by absence of a transition during said bit period. 2.A method according to claim 1, wherein said video signal is entirelydisabled during said at least one vertical field.
 3. A method accordingto claim 1, wherein the data is transmitted to the controllable videodevice during the entirety of said at least one vertical field of saidvideo signal.
 4. A video system comprising: a controllable video deviceconfigured to transmit a video signal on a transmission medium and todisable at least an active portion of the video signal during said atleast one vertical field of the video signal; and a command sourceconfigured to transmit data in separate portions to the controllablevideo device over the transmission medium during a time when said activeportion of said video signal is disabled by said controllable videodevice, each of said separate portions being transmitted on anassociated one of a plurality of horizontal lines in said verticalfield, wherein each of said separate portions comprises a plurality ofbits encoded in a bit period, a first logic value of each of said bitsbeing represented by presence of a transition during said bit period anda second logic value of each of said bits being represented by absenceof a transition during said bit period.
 5. A system according to claim4, wherein said controllable video device is configured to entirelydisable said video signal during said at least one vertical field ofsaid video signal.
 6. A system according to claim 4, wherein saidcommand source is configured to transmit the data to the controllablevideo device during the entirety of said at least one vertical field ofsaid video signal.
 7. A method of controlling a controllable videodevice configured to provide a video signal on a transmission medium,the method comprising, transmitting a function command from a commandsource to said controllable video device over the transmission medium;transmitting reply data to said command source, said reply data being inresponse to said function command and being configured to cause displayof a plurality of available functions for said controllable videodevice; transmitting a function start command to said controllable videodevice in response to said reply data, said function start command beingconfigured to cause said controllable video device to perform at leastone of said plurality of available functions.
 8. A method according toclaim 8, wherein said function command is transmitted to saidcontrollable video device in response to activation of at least one userinterface control on said command source.
 9. A method according to claim8, wherein said user interface control comprises a button on a userinterface of said command source.
 10. A method according to claim 7,wherein said reply command is configured to cause the command source todisplay a numeric value associated with each of said available functionsfor said controllable video device.
 11. A method according to claim 10,wherein said function start command comprises data representing one ofsaid numeric values associated with said at least one of said pluralityof available functions.
 12. A method according to claim 7, wherein atleast said function command and said reply data are transmitted during asingle vertical blanking period of said video signal.
 13. A methodaccording to claim 12, wherein said function command and said reply dataare each transmitted in separate portions, each of said separateportions being transmitted on an associated one of a plurality ofhorizontal lines in said vertical blanking period.
 14. A methodaccording to claim 13, wherein each of said separate portions comprises16 bits.
 15. A method according to claim 14, wherein each of said 16bits is encoded in a bit period, a first logic value of each of saidbits being represented by presence of a transition during said bitperiod and a second logic value of each of said bits being representedby absence of a transition during said bit period.
 16. A video systemcomprising: a controllable video device configured to transmit a videosignal on a transmission medium; a command source including a userinterface control for causing function command data to be transmitted tosaid controllable video device over the transmission medium, saidcontrollable video device being configured to transmit reply data tosaid command source in response to said function command, said replydata being configured to cause display of a plurality of availablefunctions for said controllable video device, wherein said reply data isconfigured to cause said command source to display a numeric valueassociated with each of said available functions for said controllablevideo device, and said command source is configured to transmit afunction start command to said controllable video device in response tosaid reply data, said function start command being configured to causesaid controllable video device to perform at least one of said pluralityof available functions, and said function start command comprises datarepresenting one of said numeric values associated with said at leastone of said plurality of available functions.
 17. A system according toclaim 16 wherein said user interface control comprises a button on auser interface of said command source.
 18. A system according to claim16 wherein said command source and said controllable video device areconfigured to transmit said function command and said reply data,respectively, during a single vertical blanking period of said videosignal.
 19. A system according to claim 16, wherein said command sourceand said controllable video device are configured to transmit saidfunction command and said reply data in separate portions, each of saidseparate portions being transmitted on an associated one of a pluralityof horizontal lines in said vertical blanking period.
 20. A systemaccording to claim 18, wherein each of said separate portions comprises16 bits, wherein each of said 16 bits is encoded in a bit period, afirst logic value of each of said bits being represented by presence ofa transition during said bit period and a second logic value of each ofsaid bits being represented by absence of a transition during said bitperiod.